El Nino caused record Carbon dioxide spike in 2015-16

The spikes recorded by OCO-2 indicated that the carbon dioxide emissions got a 50 percent increase in the year 2015-16 as compared to the average carbon emissions of preceding years.

A huge spike in carbon emissions seen in the past couple of years has puzzled scientists, since there was no evidence of a rise in human activities, like fossil fuel burning, that might explain it. For example, in tropical Indonesia a forest was burned down, which caused carbon to be released and ultimately left less plants to pull the carbon back down.

The effect was so large that it was the main factor in the biggest one-year jump in heat-trapping gas levels in the modern record, NASA scientists said.

Scientists have suspected El Nino - a weather pattern that causes sea surface temperature and air pressure in the tropical Pacific Ocean to fluctuate, and may last years at a time - might wield an influence on the balance of carbon in the atmosphere.

NASA's Orbiting Carbon Observatory 2 (OCO-2) satellite, launched in 2014, measures atmospheric carbon dioxide levels with a spatial resolution of 3 km. The findings were published Thursday in the journal Science. Researchers found that in drought-struck parts of South America plants grew less, there were more fires in Asia, and there was an increased rate of leaf decay in Africa.

"These three tropical regions released 2.5 gigatonnes (a billion tonnes) more carbon into the atmosphere than they did in 2011", said lead author of the study Junjie Liu of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. And that increase was nearly three parts per million of carbon dioxide per year or 6.3 gigatonnes of carbon. In Africa, higher than usual temperatures led plants to decompose much quicker, causing carbon dioxide to rapidly release into the atmosphere.

"Understanding how the carbon cycle in these regions responded to El Nino will enable scientists to improve carbon cycle models, which should lead to improved predictions of how our planet may respond to similar conditions in the future", said OCO-2 Deputy Project Scientist Annmarie Eldering of JPL". "In this sense, the 2015-16 El Nino is a glimpse of what is to come", Overpeck said in an email.